The following description is provided to assist the understanding of the reader. None of the information provided or references cited is admitted to be prior art.
Stem cells are cells having the ability to self-renew and divide to an unlimited extent and to differentiate under suitable circumstances to form different types of cells. Embryonic stem cells (ES cells) are stem cells established from early embryos which can be cultured over a long period of time while maintaining pluripotent ability to differentiate into all kinds of cells existing in living bodies. By contrast, somatic stem cells are any cell which is found in a developed organism that has the ability to divide and create another cell like itself and also divide and create a cell more differentiated than itself.
Induced pluripotent stem (iPS) cells are reprogrammed from somatic cells that are capable of differentiating into almost all lineages of cells. For example, it is known that skin fibroblasts may be reprogrammed into iPS. Stem cell treatments using iPS cells hold promises for treating many types of illness, such as degenerative diseases and cancer. However, reprogramming somatic cells usually results in multiple iPS clones and individual iPS clones may differ from each other, for example, in pluripotency due to different telomere lengths in individual somatic cells. Currently, assays to determine pluripotency of iPS cells requires an injection of iPS cells into Scid mice and waiting several months until the mice develop a teratoma (Brivanlou et al. (2003). Science 300, 913-916).
The field of regenerative medicine encompasses therapies designed to aid the repair, replacement, or regeneration of damaged cells, tissues, or organs. Stem cell-based therapies have the promise of treating a variety of health conditions including Alzheimer's disease, Parkinson's disease, stroke, spinal injuries, heart attack, renal failure, osteoporosis, type I diabetes, multiple sclerosis, rheumatoid arthritis, burns, and wounds. However, the progress of such therapies has been hindered by a range of factors, including the possibility of immune rejection of ES cells derived from a donor who is immunologically incompatible with the recipient. Furthermore, different lineages of stem cells are needed for treating different conditions.